Photo Courtesy of Parker/Sporlan

There are many brands and styles of evaporator pressure regulating valves (EPR), but none as common as the Parker/Sporlan SORIT and ORIT valves.

The diagram above clearly shows some of the common applications. An EPR or “hold back” valve maintains a set suction line pressure and, therefore, coil temperature. That is critical in situations where multiple evaporators of different design temperatures connect back to a shared suction header, common in grocery store refrigeration.

The EPR valve “holds back” pressure in the evaporator to a set pressure so long as there is a pressure differential between the evaporator coil and the shared suction header. The suction header must have a LOWER pressure than the lowest design pressure of any evaporator connected to it.

A SORIT valve is an EPR valve or ORIT (Open on Rise of Inlet Pressure) valve that also includes a solenoid stop.  The purpose of the solenoid stop is to prevent the defrost gas from entering the suction line and overheating/overloading the compressors when the defrost solenoid opens and back feeds the evaporator to defrost.

For a full and detailed explanation of ORIT and SORIT valves, you can read BULLETIN 90-20 from Parker/Sporlan.

—Bryan

P.S. — Matthew Taylor with Kalos Services made an entire video series about parallel racks, and Part 12 covers EPRs and SORIT valves. You can watch it at https://hvacrschool.com/videos/rack-refrigeration-cycle-part-12-epr/. His 6th Annual HVACR Training Symposium presentation was also about EPRs and how they affect the entire rack. Learn more about the symposium or purchase your virtual ticket at hvacrschool.com/symposium.